Regulation of A-type potassium channels in murine colonic myocytes by phosphatase activity

• Published in: American Journal of Physiology: Cell Physiology 2001-12, Vol.281 (6), p.C2020-C2028
• Main Authors: Amberg, Gregory C, Koh, Sang Don, Perrino, Brian A, Hatton, William J, Sanders, Kenton M
• Format: Article
• Language: English
• Subjects: Animals; Calcineurin - chemistry; Calcineurin - metabolism; Calcium - metabolism; Calcium-Calmodulin-Dependent Protein Kinases - antagonists & inhibitors; Colon - cytology; Colon - metabolism; Cyclosporine - pharmacology; Enzyme Inhibitors - pharmacology; Immunosuppressive Agents - pharmacology; Mice; Mice, Inbred BALB C; Muscle, Smooth - cytology; Muscle, Smooth - drug effects; Muscle, Smooth - metabolism; Okadaic Acid - pharmacology; Patch-Clamp Techniques; Phosphorylation; Potassium Channels, Voltage-Gated - metabolism; Protein Phosphatase 1; Sulfonamides - pharmacology; Tacrolimus - pharmacology
• ISSN: 0363-6143; 1522-1563
• DOI: 10.1152/ajpcell.2001.281.6.C2020

Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557 A rapidly inactivating K + current (A-type current) participates in the regulation of colonic muscle excitability. We found 19-pS K + channels in cell-attached patches of murine colonic myocytes that activated and inactivated with kinetics similar to the A-type current. The A-type current in colonic myocytes is regulated by Ca 2+ /calmodulin-dependent protein kinase II. Therefore, we studied regulation of the 19-pS K + channels by Ca 2+ -dependent phosphorylation/dephosphorylation. The rates of inactivation of ensemble-averaged currents resulting from 19-pS K + channels were increased by the calmodulin antagonist W-7. Inhibitors of calcineurin, cyclosporin A and FK-506, slowed the inactivation of the 19-pS K + channels. Okadaic acid, an inhibitor of the calcineurin/inhibitor-1/protein phosphatase 1 cascade, also slowed inactivation of the 19-pS K + channels. Polymerase chain reaction detected transcripts encoding calcineurin A in isolated colonic smooth muscle cells, and immunohistochemical studies demonstrated specific expression of calcineurin A-like immunoreactivity in colonic muscle tissues and in colonic myocytes. These data, when considered with previous findings, suggest that Ca 2+ -dependent phosphorylation/dephosphorylation regulates the A-type current in murine colonic smooth muscle cells. calcineurin; calcium/calmodulin-dependent protein kinase II; gastrointestinal motility